Ceramic gas discharge metal halide lamp

Abstract

A ceramic gas discharge metal halide (CDM) lamp (10) capable of retrofitting into existing high pressure iodide (HPI) metal halide and high pressure mercury vapor (HP) lamp fixtures for significient energy savings, the CDM lamp (10) having a ceramic discharge vessel (12) containing a pair of discharge electrodes (17, 18), a Penning mixture of the rare gases neon and argon, and a chemical fill which includes an oxygen dispenser and which restricts strong oxygen binders to 5 mole percent or less. In a preferred embodiment, the discharge vessel (12) has an aspect ratio R of less than 2, a wall thickness t of up to 1.2 mm, a spacing d between the discharge electrodes (17, 18) of up to 14 mm, and a passive antenna (26) on the outer wall of the discharge vessel (12), with the shortest distance a between a discharge electrode (17, 18) and the floating antenna (26) of up to 7 mm.

Description

BACKGROUND OF THE INVENTION[0001]This invention generally relates to ceramic gas discharge metal halide (CDM) lamps, and, more particularly, relates to such lamps which utilize a polycrystalline alumina (PCA) ceramic discharge vessel and a starting mixture of rare gases in the discharge space.[0002]Recently, increasing demand for reserving natural resources has led to a demand for higher efficacy lighting and lamps. For example, new energy regulations in China require a minimum efficacy of 90 lumens per watt for metal halide (MH) lamps.[0003]The High Pressure Iodide (HPI) metal halide lamp, which has been in the market for over forty years, offers white light and long life and thus has multiple lighting applications. It is especially popular in Europe and Asia. However, the efficacy of HPI lamps is in the moderate range of 80 lumens per watt. The efficacy of high pressure mercury vapour (MV or HP) lamp is even lower (e.g., 57.5 lumens per watt for clear lamps and 45 lm / W for phospho...

AI Technical Summary

Benefits of technology

[0011]The presence of the oxygen dispenser together with the limited amount of strong oxygen binders enables a process known as tungsten re-generation to occur in the discharge vessel during lamp operation. The process is enabled when sufficient vapour pressure of WO2I2 exists near the wall of the discharge vessel to prevent tungsten crystal growth on the wall. At the high temperatures generated by the plasma stream of the arc discharge, WO2I2 decomposes and tungsten deposits back onto the electrodes. As a result, the discharge wall remains clean, and the lumen maintenance for the lamp is not negatively affected by the presence of the relatively light gas mixture of neon-argon.

[0014]Because of the formation of efficient Penning mixtures between neon and argon, the lamp can start at much lower voltage provided by a ballast without an ignitor. Unlike the argon-mercury mixture that relies on Hg pressure which has very low vapour pressure at low temperature, the neon-argon Penning mixture is not affected by low temperature. So the neon-argon gas filled lamp can reliably start at cold and dark environment.

Problems solved by technology

U.S. Pat. No. 6,833,677 discloses a ceramic gas discharge metal halide (CDM) lamp having a power of from 150 W to 1000 W. These lamps can retrofit into high pressure sodium (HPS) or pulse start quartz metal halide (QMH) sockets, but are not suitable retrofits for HPI or HP lamps.

However, the use of xenon gas tends to increase the lamp ignition voltage.

The disadvantage of argon gas is that argon atoms are smaller than xenon atoms, and thus argon is not as good as xenon in suppressing tungsten sputtering from the electrodes, and preventing tungsten atoms from reaching the walls of the discharge vessel.

As a result, wall blackening occurs and lumen maintenance is lower for argon-filled lamps as compared to xenon-filled lamps.

However, this mixture of predominately light atoms of neon is even less efficient than pure argon in suppressing tungsten sputtering, and thus the lumen maintenance for lamps filled with light gases such as the neon-argon Penning mixture is even lower than that of lamps employing the heavier atoms argon and xenon.

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